We have previously discovered Si-granules in mitochondria of diatoms and rat liver, kidney and spleen. To understand their possible role in mineralization (bone formation or diamond wall formation), their production and relationship to calcium phosphate granules found in animal mitochondria will be investigated. The following studies will be conducted: Formation of Si-granules (1) in rats pre-loaded with silicic acid; (2) in vitro, in rat mitochondria; and (3) in synchronized cultures of diatoms during wall formation. BIBLIOGRAPHIC REFERENCES: C.W. Sullivan and B.E. Volcani. Multiple ion-stimulated adenosine triphosphatase activities associated with membranes of the diatom Nitzschia alba. Arch. Biochem. Biophys. 167: 437-443 (1975). C.W. Mehard and B.E. Volcani. Evaluation of silicon and germanium retention in rat tissues and diatoms during cell and organelle preparation for electron probe microanalysis. J. Histochem. Cytochem. 23: 348-358 (1975).